This effort develops and tests algorithms and a user-portable optical system designed to autonomously optimize the laser communication wavelength in open and coastal oceans. In situ optical meteorology and oceanography (METOC) data gathered and analyzed as part of the auto-selection process can be stored and forwarded. The system performs closedloop optimization of three visible-band lasers within one minute by probing the water column via passive retroreflector and polarization optics, selecting the ideal wavelength, and enabling high-speed communication. Backscattered and stray light is selectively blocked by employing polarizers and wave plates, thus increasing the signal-to-noise ratio. As an advancement in instrumentation, we present autonomy software and portable hardware, and demonstrate this new system in two environments: ocean bay seawater and outdoor test pool freshwater. The next generation design is also presented. Once fully miniaturized, the optical payload and software will be ready for deployment on manned and unmanned platforms such as buoys and vehicles. Gathering timely and accurate ocean sensing data in situ will dramatically increase the knowledge base and capabilities for environmental sensing, defense, and industrial applications. Furthermore, communicating on the optimal channel increases transfer rates, propagation range, and mission length, all while reducing power consumption in undersea platforms.
Free-space laser communications are subjected to performance degradation when heavy fog or smoke obscures the line of sight (high-loss optical media). On the other hand, it has been demonstrated that laser-induced plasma filaments (LIPF) can propagate for long distances (up to a few kilometers) through clouds and/or turbulent (lossy) atmosphere. Here we propose to use LIPF to improve and/or restore laser communication in adverse, high-loss and/or denied conditions. This work is focused on demonstrating the proof of concept and is dedicated primarily to gaseous, optically transparent media.
This paper describes a novel technique for the detection of contaminants in air using the process of laser-induced filamentation. This work is focused primarily on the visible and infrared spectrum. Characterization of the temporal and spatial evolution of laser-generated plasma in solvent aerosols is necessary for the development of potential applications. Atmospheric aerosols impact capabilities of applications such as range from laser-induced ionized micro channels and filaments able to transfer high electric pulses over a few hundreds of meters, to the generation of plasma artifacts in air, far away from the laser source.
We discuss single-photon counting technologies, in particular at the optical wavelength of 1550 nm and their application in quantum communication. In particular we discuss the case of quantum cryptography illustrating with experiments performed in our lab, supplemented by recent experiments by other groups. We furthermore discuss briefly more general protocols for quantum communication and address some experimental changes.
Hydroxyapatite (HA), Ca10(PO4)6(OH)2, is the primary constituent of the human bone and one of the best biocompatible materials. In this work we developed a simple method for the deposition of polycrystalline HA thin films onto various collectors including substrates of medical interest (e.g. Ti). We proceeded by the pulsed laser deposition of HA targets onto parallel collectors placed at (2-5) cm in vacuum. After deposition the films were heated in air at 500 degree(s)C for 30 minutes. The heated film has a structure which appears in electron diffraction as identical to the structure of the base material. The obtained films are uniform and very adherent to the substrate. The P/Ca atomic ratio, determined by energy dispersive X-ray analysis, was found to be close to that characteristic to HA, for the post-depositing heated films.
A normal and a tumoral chromatin radiosensitivity to an UV laser radiation was determined. The characteristics of these chromatin samples were established by the analysis of the absorption and emission spectra of chromatin complexes with a specific DNA ligand-ethidium bromide, by Scatchard representations of ligand binding to chromatin and by the Forster energy transfer efficiency determination between two fluorescent ligands coupled at chromatin: dansyl chloride and acridine orange. The effects of excimer laser beam with (lambda) equals 248 nm on chromatin structure were analyzed by the above methods and also by the establishment of the intrinsic chromatin fluorescence and of the excited state lifetimes of a specific DNA ligand.